What classification does the letter 'M' signify in cohesive soils?

• A. Gravel
• B. Sand
• C. Silt
• D. Clay

Answer: (C)

The letter 'M' in the context of cohesive soil classification designates silt. According to the Unified Soil Classification System (USCS), soil types are identified with specific letters based on their grain size and plasticity characteristics.

In this classification, 'M' represents silt, which is a fine-grained soil material that can retain moisture and is plastic when wet. Silts are typically characterized by their ability to be shaped and molded when wet, but they possess less plasticity compared to clay soils, which are categorized under the letter 'C'. Understanding this classification is essential for soil testing practices, as it influences the behavior and stability of soils in engineering and construction applications.

This designation also differentiates silts from coarser materials like gravel and sand, which are associated with other letters in the classification system. Recognizing these distinctions helps professionals choose appropriate methods for handling, testing, and utilizing different soil types.